Ah, I was looking at the wrong package. Searching for glibc in Synaptic does not find the actual glibc packages, which confused me.

It looks like this is a regression in the latest eglibc package in the Ubunbu updates repository (the date matches). Apparently Ubuntu had previously backported the fix from 2.23. So this appears to be a problem with the Ubuntu patches to EGLIBC 2.19. I will report the problem to them. (The way they organize their repositories, I doubt that a different version would be associated with Ubuntu 14.04.4)

From:        "adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org>
To:        friesens@gdls.com,
Date:        06/03/2016 09:04 AM
Subject:        [Bug math/19439] Unix98 isinf and isnan functions conflict with C++11


--- Comment #18 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
You are still confusing things. There is no glibc version 3.13.0-86.131, it is
most likely the *kernel* version.  Ubuntu 14 ships EGLIBC 2.19 if I recall

Now, to correct your problem you will need to check with Canonical to see if it
either already update GLIBC with this fix or to open a request to do so.
Latest Ubuntu 14 is 14.04.4, so you might try to check this update.

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